Week 6 ---Summary of Object-Oriented Programming Concepts

Object-oriented programming is based on the concept of object. This definition is taken from Wikipedia and tells me almost nothing at first when I google it. It can't be clear without some solid example. Here is some of my personal thoughts on OOP.  For example, python classes have all features of OOP. In python, class defines what is common for a whole class of objects. If we define a class 'Point'(like we did in the lecture), this doesn't imply we create an arbitrary point, but implies we create a kind of manual instruction of constructing 'Point' objects, and this manual instruction is completely up to us to decide. For example , '(3,4) is a point' in python language is '(3,4) is an instance of Point class'. We need to initialize 'Point' and creating attributes like coordinate(its distance from original point (0,0)).

Creating 'Point' class, we haven't create any point. We only create a sort of rules for what it means to be a point. No point exists until we call Point(). For example, >>> p = Point(3.0, 4.0). This implies that we use Point class rules to create a new object, this object is referred as p.

There are many methods we can use to make our class more practical. For example, __str__, __eq__, __repr__  .

One very powerful concept is inheritance. The concept itself is very self-explanatory. The idea is that subclass inherited the method and data from superclass.

For example, if we run a bookstore, we sell many types of books from fiction to non-fiction. We want to record the sales of each type books; we want to apart the fiction from non-fiction books. We create a super class Book, and we write a function sales() in the function with 'NotImplementedError'. Then we create subclass for each type of books. One sub for fiction, one for non-fiction, etc. In each subclass, we again write the function sales() with some specific instructions.